1. Field of the Invention
The invention relates to a steam generator with a pressure-tight pressure casing which encloses a volume and in which extends at least one hollow tube which is hermetically sealed in relation to the volume, which hollow tube is connected in each case to a feed section and a discharge section which project through the pressure casing in a fluidtight manner, wherein at least one opening for feed of a heat flow into the volume, and also at least one opening for outlet of the heat flow, which engages in thermal interaction with the at least one hollow tube, is provided in the pressure casing.
2. Brief Description of the Related Art
Steam generators of the aforementioned generic type serve preferably for thermal coupling in a combined gas-steam turbine arrangement in which the hot air which issues from the compressor of the gas turbine plant is fed to a steam generator system where it is cooled so much so that it can be fed back into the gas turbine for cooling purposes. The steam generator draws the water from the economizers of the waste heat boiler and feeds the steam which is produced into the superheater of the waste heat boiler, from where it is directed through the steam turbine for expansion.
For steam production, especially for the purpose of power production, steam generator systems which are as flexible as possible are used, of which the concept of so-called once-through coolers (OTC) is subsequently elaborated upon. The so-called OTC systems have cylindrically formed pressure casings of high construction, the standing height of which clearly projects beyond the gas turbine. Inside the cylindrically formed pressure casing, which is formed with pressure-tight effect, such OTC coolers have water-carrying pipes which are formed helically around the longitudinal axis of the cylinder and which are spatially fixed by means of so-called perforated support plates, with only a small mutual radial spacing. For illustration of such a cooler arrangement, refer to the representation in FIG. 2, in which a tube bundle arrangement is apparent, which can be introduced inside a pressure-tight, cylindrically formed pressure casing, which is not shown. The hollow tube arrangement, which is shown in the representation in FIG. 2, is horizontally arranged for assembly purposes, and in the case of normal use would be erected vertically upright inside the pressure casing, which is not shown. In this connection, the section which is shown on the right in the pictorial representation corresponds to the upper section. The representation in FIG. 2 is basically the helical multiple arrangement of individual hollow tubes 1 around a common cylinder axis Z, which tubes are all wound radially around the cylinder axis Z in the form which is represented, with a high, mutual packing density. Radial support plates 2, which are arranged in sectors in a distributed manner around the cylinder axis Z, and which provide a plurality of perforations which are defined on the outside diameter of the individual hollow tubes and through which the hollow tubes 1 are to be threaded for assembly purposes, serve for spatial fixing and mutual spacing of the individual hollow tubes 1. It requires no further explanation that the assembly alone of the hollow tube arrangement which is shown in FIG. 2 is extremely time-consuming and, therefore, costly.
For steam production, water is fed through the hollow tubes 1 in such a way that the hollow tubes 1 are flow-washed from the left-hand side to the right-hand side of the hollow tube arrangement in the figure, while the hollow tube arrangement is flow-washed by hot air of a gas turbine arrangement, which is not additionally shown, in the reverse direction, i.e., from the right-hand side to the left-hand side in the pictorial representation. This flow configuration corresponds to the reverse flow principle and allows the water which is fed into the hollow tubes in the bottom, i.e., on the left-hand side, of the hollow tube arrangement in the figure, to be effectively heated until it evaporates inside the individual hollow tubes 1 in the right-hand section of the hollow tube arrangement. All the hollow tubes, in the upper section of the steam generator, i.e., in the right-hand section in FIG. 2, lead into the so-called steam collector D, from which the steam is user-specifically discharged. In the case of a combined gas turbine plant, the steam generator arrangement shown in FIG. 2 serves to drive a steam turbine and for the corresponding conversion into electrical energy.
In addition to the aforementioned high costs for production of such a steam generator, the exceedingly large overall height of the steam generator, which is to be erected vertically, also encounters constructional and system technical problems, particularly that it is not possible for space reasons to position such steam generators spatially close to those points of a gas turbine plant at which hot air can be tapped for steam production. The consequence is a comparatively large distance between such a steam generator system and the gas turbine plant, as a result of which connecting pipes of long construction are necessary in order to bring the hot air flows to the corresponding feed points of the steam generator. This, however, inevitably leads both to thermoenergetic losses and to pressure losses along the respective connecting pipes, as a result of which the efficiency for steam production is ultimately significantly impaired.